1. Field of the Disclosure
The technology of the disclosure relates to cooling systems and related components and methods.
2. Technical Background
Wireless communications are subject to increasing demands for high-speed mobile data communications. “Wireless fidelity” or “WiFi” systems and wireless local area networks (WLANs) are now deployed in many different types of areas to provide wireless services. Distributed antenna systems also provide a variety of wireless services by communicating with wireless devices called “client devices” which must reside within the wireless range or “cell coverage area.” Distributed antenna systems are particularly useful inside buildings or other indoor environments where client devices may not otherwise receive radio frequency (RF) signals. Distributed antenna systems have RF antenna coverage areas, also referred to as “antenna coverage areas,” having a relatively short range.
FIG. 1 is a schematic diagram of an optical fiber-based distributed antenna system (DAS) 10. The system 10 generates antenna coverage areas for establishing communication with wireless client devices located within the RF range of the antenna coverage areas. The DAS 10 includes a central unit or head-end unit (HEU) 12, remote antenna units (RAUs) 14, and an optical fiber link 16 that couples the HEU 12 to the RAU 14. The HEU 12 receives communications over downlink electrical RF signals 18D from a source or sources and provides the communications to the RAU 14. The downlink communication signals are received through a downlink input. The HEU 12 is also configured to return communications received from the RAU 14, via uplink electrical RF signals 18U, back to the sources. The optical fiber link 16 includes downlink optical fibers 16D to carry signals communicated from the HEU 12 to the RAU 14 and uplink optical fibers 16U to carry signals communicated from the RAU 14 back to the HEU 12. An interface couples the HEU 12 to the optical fiber link 16 by receiving downlink signals and passing them to the RAU 14 through the link 16.
The DAS 10 has an antenna coverage area 20 that can be substantially centered about the RAU 14. The antenna coverage area 20 of the RAU 14 forms an RF coverage area. The HEU 12 performs a number of Radio-over Fiber (RoF) applications, such as radio-frequency identification (RFID), WLAN communication, and cellular phone service. Client devices 24 in the coverage area 20 can be mobile terminals such as cellular telephones, smart phones, or tablet computers. The client device 24 includes an antenna 26 for receiving and/or sending RF signals. The HEU 12 includes an electrical-to-optical (E/O) converter 28 to communicate downlink electrical RF signals over the downlink optical fiber 16D to the RAU 14, to in turn be communicated to the client device 24 in the antenna coverage area 20 formed by the RAU 14. The E/O converter 28 converts the downlink electrical RF signals 18D to downlink optical RF signals 22D to be communicated over the downlink optical fiber 16D. The RAU 14 includes an optical-to-electrical (O/E) converter 30 to convert received downlink optical RF signals back to electrical signals to be communicated wirelessly through an antenna 32 to client devices 24 located in the antenna coverage area 20. The antenna 32 receives wireless RF communication from client devices 24 and communicates electrical RF signals representing the wireless RF communication to an E/O converter 34 in the RAU 14. The E/O converter 34 converts the electrical RF signals into uplink optical RF signals 22U to be communicated over the uplink optical fiber 16U. An O/E converter 36 in the HEU 12 converts the uplink optical RF signals 16U into uplink electrical RF signals, which are then communicated as uplink electrical RF signals 18U back to a network. The RAU 14 can include a controller 40 to facilitate one or more operations of the RAU.
DASs and other wireless systems are usually fed by a base station, a repeater, or other RF source that provides output power in a specified range. Since DAS equipment is usually designed to operate with lower input power than that of the source, the signal is attenuated between the DAS and the source. Since attenuators may need to dissipate high power, they are often cooled by fans. Failures of such fans can result in damage caused by electronic components.